Various systems and methods exist for determining properties of multi-component gases. The gas' heating value, energy flow, mass flow and the like are typical properties of interest. Before a natural gas transmission pipeline company transfers or sells natural gas to distribution companies, the energy content in the natural gas has to be determined within a certain accuracy. Also, the energy measurement is preferred to be on-line during the transfer and in real time. Additionally, a fast and accurate determination of energy in the fuel line of a natural gas turbine would provide for optimal combustion.
Traditionally, energy content in natural gas is calculated from a complete gas analysis through gas chromatography. Gas chromatography is mostly an “off-line” analysis with a slow response time. Its operational cost is high due to required consumables and frequent calibrations.
Also, some known systems for determining gas properties without a complete gas analysis typically make determinations based on limited or fixed, not dynamic, correlations between various components and properties of the gas. U.S. Pat. Nos. 6,850,847 and 6,216,091, which are each incorporated herein by reference, are some examples of known methods. See, e.g. www.elster-instromet.com/downloads/ELS_GM_EnSonic_DS_UK_ol_l.pdf, which is incorporated herein by reference.
The challenge is to determine a gas' energy, such as heating value and other properties, more accurately, in real time, and at low cost.